Stabilization system for liquid cargo ships



March 10, 1970 s. B; FIELD ETAL STABILIZATION SYSTEM FOR LIQUID CARGO SHIP S Filed Aug. 5, 1964 M v O I H. M L I w. m, ww ul 1 F M m r Y B m N. pm Hull 1 w I ME 5 Z .wv 1W II|H N O 0 v 0 aw M mfi k m /MflmW/M ATTORNEYS March 10, 1970 s. BIFIELD .ETAL

STABILIZATION SYSTEM FOR LIQUID CARGO SHIPS 5 Sheets-Sheet 2 Filed Aug. :5, 1964 INVENTORS eld, Thom F. Bridges ,8 ',%%&;M ATTORNEYS amt 82% 234 ifiamxmq $33 mm mm March 10, 1970 s. HE ErAL 3,499,410

STABILIZATION SYSTEM FOR LIQUID CARGO SHIPS 5 Sheets-Sheet 3 Filed Aug. 5, 1964 ih 1.1m In Ill. mml.

INVENTORS Jkedom 5 Field, Thoma A 57@6$ ORNEYoi March 10, 1970 s, H ETAL STABILIZATION SYSTEM FOR LIQUID CARGO SHIPS '5 Sheets-Sheet 4,

Filed Aug. 3, 1964 INVENTORS- Skaldarz 5. Field,

Thomas F. 5r

I ATTORNEY6 March 10, 1970 5, H EI'AL 3,499,410

SIABILIZATION SYSTEM FOR LIQUID CARGO SHIPS Filed Aug. 5, 1964 5 Sheets-Sheet 5 INVENTORS Sheldon B, FeZd,

ATTORNEY? United States Patent 3,499,410 STABILIZATION SYSTEM FOR LIQUID CARGO SHIPS Sheldon B. Field, Floral Park, and Thomas F. Bridges,

Port Washington, N.Y., assignors to John J. McMullen Associates, Incorporated, New York, N.Y., a corporation of New York Filed Aug. 3, 1964, Ser. No. 386,982

Int. Cl. B63b 25/12, 43/04 U.S. Cl. 114-125 3 Claims This invention relates to a passive stabilization system and more particularly to such a stabilization system for water going tankers which are adapted to transport a liquid cargo, or the like, therein.

It is customary today for water going liquid cargo tankers to have a plurality of transverse and longitudinal compartments defined by a plurality of longitudinal and transverse watertight bulkheads which form the skeleton or structural framework of the tanker. These bulkheads are usually watertight so that liquid or cargo flow between compartments is prevented. The purpose of this is to prevent an accumulation of fluid at one side of the tanker to prevent list or instability of the tanker.

It is a primary object of the present invention to provide a fiume type passive stabilization system in cargo tankers which basically is comprised of the existing structural elements of the tanker. This is accomplished by placing a plurality of elongated holes or panel cuts in the existing bulkhead arrangement of the tanker to enable a controlled and predetermined amount of liquid cargo to flow or transfer between the sections defined by said bulk heads in response to the roll motion of the tanker.

It is another object of the present invention to out said aforementioned holes in such a manner and with such a shape as to enable fluid transfer without weakening to a substantial degree the structural and supporting functions of the bulkheads.

It is another object of the present invention to provide in combination with said aforementioned bulkheads a plurality of stitfeners mounted on the longitudinal bulkhead, said stilfeners enabling said bulkhead to;withstand the great pressures and forces applied thereto.

It is yet another object of the present invention to incorporate a single longitudinal upright member with a plurality of elongated holes or panel cuts therein which comprise the fluid energy damping means for the stabilization system.

Other and further objects of the present invention will become apparent with the following detailed description when taken in view of the appended drawings in which:

FIG. 1 is a side elevation partially in section of a liquid cargo tanker showing one example of the location of the passive stabilization system;

FIG. '2 is a vertical transverse section taken along line 22 of FIG. 1;

FIG. 3 is a vertical longitudinal section taken along line 3-3 of FIG. 2 and illustrates the section of a longitudinal bulkhead located within the stabilizer system;

FIGS. 4 and 5 are side elevation views of some of the elongated holes or ports cut in the longitudinal bulkheads;

FIG. 6 is a vertical section taken on line 66 of FIG. 4;

FIG. 7 is a top plan view of the cargo section of another type of vessel with large cargo or ballast tanks;

FIG. 8 is a vertical transverse section taken along line 8-8 of FIG. 7; and

FIG. 9 is a vertical longitudinal section taken on line 99 of FIG. 8, showing the central upright damping plate having elongated holes and ports cut therein.

Referring now to FIG. 1 in detail, there is illustrated a tanker 10 having an engine and quarter section 12 and a cargo section 14. Said cargo section 14 is divided into a plurality of compartments by transverse watertight bulkheads 16 and two parallel longitudinal bulkheads 18.

In this example, the passive type stabilization system is located in cargo tank 4, said stabilization system being generally indicated as 20 and illustrated in schematic in FIG. 1.

Referring now to FIGS. 2 and 3, it can be seen that longitudinal bulkheads 18 extend from the top to the bottom of the liquid cargo area and have a plurality of elongated openings or panel cuts therein. There are basically three (3) types of cuts or openings in the longitudinal bulkheads 18. There are the short cuts 22 which have a predetermined longitudinal dimension, long cuts 24 which have a longitudinal dimension approximately twice that of the short cuts, and short openings 26, one end of which is semi-circular and the other end of which is elliptical.

The purpose of the elliptical end of short openings 26 is to provide the maximum opening for liquid transfer therethrough and at the same time provide for maximum structural design so that the solid portion of the longi tudinal bulkhead does not experience great stresses in the areas near the ends of the lowermost cuts. The purpose of the different dimensions for openings 22 and 24 is also a structural one so that optimum liquid transfer is provided without a detrimental loss in structural design of the longitudinal bulkhead. It can be seen in FIG. 3 that the short openings 26 have a plurality of locations which are progressively more centrally and downwardly located within the longitudinal bulkhead. Once again, this is done for structural reasons so that the bulkhead can withstand its own weight, and the additional forces applied thereto when fluid is transferring therethrough.

The panel cuts are disposed in upper and lower groups, said groups being vertically spaced from each other.

The stabilization system is defined on one side by bulkhead 28 and on the other by bulkhead 30. Bulkhead 32 defining cuts 36 and a plurality of structural webs 34 defining cuts 38 are located transversely in the tanker, and provide for additional structural support.

A plurality of bulkhead stiffeners in the form of I- beams or L-beams 42 are mounted longitudinally and in parallel relationship with each other on the solid parts of longitudinal bulkheads 18. These stiffeners 42 provide the structural strength to the bulkhead 18 which opposes the great forces and pressures applied to said bulkheads 18 by the transferring fluid therethrough. Furthermore, great pressures will be exerted normal to said bulkhead by the potential hydrostatic head formed by the liquid in the raised side compartments of the tanker when the tanker experiences a roll condition. As better seen in FIG. 2, the stiifeners 42 have an increasingly greater transverse dimension as the locations of said stiifeners 42 are viewed from top to bottom. The reason for this design is that the pressures or forces at the top of the bulkhead 18 will be much less than the pressures and forces acting on the bottom of said bulkhead 18. Therefore, greater strength reinforcement is needed at the bottom than at the top.

A row of circular cuts 44 are defined in bulkheads 18 above the topmost stiffener 42.

The operation of the system shown in FIGS. 1-6 will now be described. It will first be assumed that the tanker is operating with the liquid level in the ballast condition within the cargo section 14 of the vessel. As illustrated in FIG. 2, the liquid level-ballast condition is located slightly below the upper limit of the area of panel cuts for the lower group of cuts. As the tanker rolls to lower the right side thereof, as seen in FIG. 2, the liquid within the stabilization system flows through the lower group of panel cuts so that fluid mass accumulates at the right section of the stabilizer. As the liquid flows through the longitudinal bulkheads 18, a portion of the kinetic energy of said fluid is dampened by the fluid motion impedance imparted by the stationary bulkheads 18. As the tanker reaches its maximum degree of roll and begins to roll in the opposite direction so that the right side thereof is rising toward horizontal, the accumulated fluid mass in the right section of the stabilizer imparts a stabilizing moment to the tanker which opposes the roll of the tanker.

After the tanker rolls through the horizontal position and the right side thereof continues to rise, the fluid mass within said right section forms a hydrostatic head and the liquid now flows to the left through the lower panel cuts in bulkheads 18 toward the opposite side of the tanker. The external forces or waves striking the tanker impart a certain amount of kinetic energy to the moving fluid. Said kinetic energy is dampened as the liquid within the stabilizer passes through the area of panel cuts within said bulkheads 18.

Again, after the left side of the tanker reaches its lowermost position and begins to rise and approach the horizontal position, the accumulation of liquid mass at the left side thereof imparts a stabilizing moment to the vessel in opposition to the roll thereof.

It can be seen that when the liquid level of the ballast condition is well below the upper limit of the lower panel cuts, the air space above the liquid in the stabilization system is enabled to freely pass through the respective bulkheads through the cuts above the liquid level. If the tanker is experiencing great degrees of roll with the liquid level at ballast condition, the liquid level will exceed the top line of cuts in the lower group of the bulkhead. However, the air in the right section is still enabled to freely communicate with the other areas of the stabilization system through the upper group of panel cuts of bulkhead 18 and air passages provided at the top of the bulkhead.

Now let it be assumed that the tanker is operated under full load condition as indicated by the upper liquid level better seen in FIG. 2. The operation of the system during small magnitude rolls of the tanker is substantially the same as that described above. However, all the liquid transfer between the relative sections of the stabilizer takes place in the area cuts substantially below the liquid level of the full cargo load condition. Furthermore, the air space above the liquid level is again unthrottled due to the free air communication through the panel cuts located in the upper group.

Let it now be assumed that the liquid level is at the full load condition and the degree of tanker roll is substantially great so that the liquid level rises to the upper panel cut area. In this condition, there will again be substantial amounts of liquid transfer through the lower group of panel cuts in longitudinal bulkheads 18, but in addition, there will be a spillover liquid transfer through the panel cuts in the upper group of bulkheads 18. Since the vertical dimension of the panel cuts is about one and a half feet, it is anticipated that the upper cuts will be completely covered by liquid transferring therethrough. Therefore, the liquid spillover in the upper cuts will take place through the entire vertical dimension of said cuts. However, the system enables air to be freely transferred through the bulkheads, notwithstanding the spillover through the upper panel cuts, by use of several round air passage holes 44 cut in the upper portions of bulkheads 18.

There has been described an eflicient passive stabilization system which imparts a stabilizing moment to a tanker carrying liquid cargo by enabling liquid transfer through various compartments of said tanker, said transfer being controlled by a plurality of panel cuts defined in said tankers existing bulkhead framework. It is obvious that the number of stabilization systems and the location of the stabilization systems for a liquid carrying tanker can be varied without departing from the spirit of the present invention.

Referring now to FIGS. 7, 8 and 9, there is shown another embodiment of the present invention. The transverse structural webs, defined herein below, have been omitted from FIG. 7 for the purpose of clarity. The tank section of ship 50 comprises two vertically disposed longitudinal bulkheads 52 and 54 running substantially the entire length of the tanker. A plurality of transverse bulkheads define with bulkheads 52 and 54 a plurality of sections or individual compartments throughout the ship. As more clearly seen in FIG. 8, a lower deck 58 is mounted horizontally throughout and divides said ship in the vertical plane.

As can be seen in FIG. 8, a plurality of centralized watertight compartments 60 are defined in the central bottom portion of the ship. Compartments 60 are defined by bulkheads 52 and 54 which form the ends thereof and transverse bulkheads 56 which comprise the sides thereof, the bottom of the ship 62 which comprises the bottom of the stabilization tank and the lower deck 58 which comprises the top. A bulkhead or panel 64 is vertically mounted along the center line of the ship and extends from the lower deck 58 to the bottom of the ship 62 and longitudinally (laterally for tank 60) between two respective transverse bulkheads 56. The upright panel 64 defines therein a plurality of elongated panel cuts 68 disposed in a plurality of rows and columns and an upper row of circular panel cuts 70 and a lowermost row of circular panel cuts 72. Panel cuts 70- and 72 are circular because of structural reasons, and said design prevents great stresses within bulkhead 64.

A plurality of transverse structural webs 74 are mounted within tank 60 between bulkheads 52 and 54 and function to aid the structural function of central bulkhead 64. A plurality of I- or L-beams mounted longitudinally on the solid ribs of bulkhead 64 act as stiifeners as described above.

The tank type stabilization systems 60 are, in this instance, located in tanks No. 1, 2, 3, 4, 6 and 7, and each has a body of liquid therein which is distributed between the two sections of each stabilizer 60, said body of water or other liquid partially filling the said stabilizer 60 and having a volume which is substantially equal to the ballast volume for the ship. As can best be seen in FIG. 8, the other sections of the ship, that is, sections 76, 78, 80, 82 and 84 are adapted to be used for storing and transporting liquid in the conventional manner. Liquid flow between the sections 76 to 84 is prevented by the solid bulkheads 52, 54 and transverse bulkheads 56 and lower deck 58.

The ballast or stabilizing liquid can be of any suitable type notwithstanding the type of liquid being transported or stored. If desired, said stabilizing liquid could be reserve oil or fuel, ballast or a suspension, which need only be used in an emergency.

The operation of the stabilizer shown in FIGS. 7-9 will now be described. As the right side of the ship is lowered due to the roll of the ship, the liquid within compartment 60 begins to move toward the right side of compartment 60- through the upstanding vertically disposed bulkhead 64. As the liquid is transferred through the panel cuts of bulkhead 64, a portion of the kinetic energy thereof is dampened by the throttling action of said panel cuts on the moving fluid. After the right side of the tank reaches its lowermost position and begins to rise to the horizontal, the accumulation of a fluid mass in the right side of compartment 60 imparts a restoring moment to the ship which opposes the rolling of the vessel. As the ship continues to roll through the horizontal position and the right side continues to rise, a hydrostatic head is formed by the accumulated fluid mass within the right side of compartment 60 and the fluid begins to transfer toward the left side of said compartment, again through the panel cuts of bulkhead 64. Again, as the liquid transfers through said bulkhead, a portion of the kinetic energy thereof is dissipated by the throttling action of said panel cuts. After the tanker reaches its maximum degree of roll and the left side thereof begins to rise toward the horizontal, the accumulation of fluid mass at the left side of compartment 60 imparts a stabilizing moment to the ship which opposes the roll of the ship.

In view of the fact that the liquid level is substantially below the top (that is, lower deck 58) of compartment 60, the air above said liquid is enabled to freely transfer through the panel cuts within bulkheads 64. It is further pointed out that there is a substantial amount of fluid transfer between the two sections defined by compartment 60 and the center bulkhead 64 so that the maximum stabilizing moment can be imparted to the vessel.

It is further pointed out that the only fluid energy damping means is located in the center of compartment 60 and comprises the existing bulkhead structure of the ship so that there is no requirement of adding additional structure for stabilization purposes. Furthermore, the stabilization function is performed by the liquid medium so that no additional liquid is necessary for stabilization purposes other than that normally carried by the ship as ballast or cargo.

Therefore, it can be seen that an economical, advantageous, efficient and rugged stabilization system can be incorporated in a ship without the addition of great amounts of structural material to form the stabilization system. Other and further modifications can be made to the present invention without departing from the spirit thereof.

What is claimed is:

1. A liquid cargo tanker comprising a plurality of transverse liquid tight bulkheads mounted within the hull and forming therewith a plurality of compartments, a pair of longitudinal bulkheads symmetrically mounted in said hull, and being spaced from the centerline and hull sides all said bulkheads extending to the main deck of said tanker, a horizontal tween deck mounted between said longitudinal bulkheads and forming with the hull bottom, adjacent transverse bulkheads and longitudinal bulkheads an enclosed passive stabilizer tank, which is 5 bounded on three sides by liquid tight cargo subcompartments, at least one additional longitudinal bulkhead spaced from said pair of longitudinal bulkheads and mounted across said stabilizer tank and extending vertically from the hull bottom to the tween deck, said additional bulkhead having a plurality of openings spaced throughout the vertical dimension thereof, and a liquid body partially filling said stabilizing tank to a static liquid level which is above some of the openings and below others of said openings. 15 2. A tanker as set forth in claim 1, wherein a plurality of said stabilizer tanks are provided in said tanker such that the total weight of stabilizing liquid bodies is sufficient to properly ballast the tanker when all cargo is removed therefrom.

3. A tanker as set forth in claim 1, wherein the liquid in the stabilizer tank is of a type other than the cargo to be carried.

References Cited 25 UNITED STATES PATENTS 3,103,198 9/1963 Ripley 114 12s 3,164,120 1/1965 Field 114 12s 3,260,231 7/1966 Hilliard 114-425 20 FOREIGN PATENTS 688,796 3/1940 Germany.

TRYGVE M. BLIX, Primary Examiner US. Cl. x1 114-74 

1. A LIQUID CARGO TANKER COMPRISING A PLURALITY OF TRANSVERSE LIQUID TIGHT BULKHEADS MOUNTED WITHIN THE HULL AND FORMING THEREWITH A PLURALITY OF COMPARTMENTS, A PAIR OF LONGITUDINAL BULKHEADS SYMMETRICALLY MOUNTED IN SAID HULL, AND BEING SPACED FROM THE CENTERLINE AND HULL SIDES ALL AND BULKHEADS EXTENDING TO THE MAIN DECK OF SAID TANKER, A HORIZONTAL TWEEN DECK MOUNTED BETWEENEN SAID LONGITUDINAL BULKHEADS AND FORMING WITH THE HULL BOTTOM, ADJACENT TRANSVERSE BULKHEADS AND LONGITUDINAL BULKHEADS AN ENCLOSED PASSIVE STABILIZER TANK, WHICH IS BOUNDED ON THREE SIDES BY LIQUID TIGHT CARGO SUBCOMPARTMENTS, AT LEAST ONE ADDITIONAL LONGITUDINAL BULKHEAD SPACED FROM SAID PAIR OF LONGITUDINAL BULKHEADS AND MOUNTED ACROSS SAID STABILIZER TANK AND EXTENDING VERTICALLY FROM THE HULL BOTTOM TO THE TWEEN DECK, SAID ADDITIONAL BULKHEAD HAVING A PLURALITY OF OPENINGS SPACED THROUGHOUT THE VERTICAL DIMENSION THEREOF, AND A LIQUID BODY PARTIALLY FILLING SAID STABILIZING TANK TO A STATIC LIQUID LEVEL WHICH IS ABOVE SOME OF THE OPENINGS AND BELOW OTHERS OF SAID OPENINGS. 